The present invention relates to a honing device for the precision boring of small bores into workpieces.
In honing devices of this type, reference being made to Federal Republic of Germany Utility Model No. 83251049, for example, it is already known to feed the coolant in a controlled way into the work zone of the honing tool. There is an axial coolant duct which opens out directly into the work zone via radial bores. The coolant is fed via a coolant distributor arranged above a clamping point of the tool body. It is guided on a connecting tool attached to the honing tool and is held so as to be axially immovable. The connecting tool has a further clamping end which is located opposite the clamping end of the honing tool and which can be clamped in a drill chuck or the like of a machine tool.
The disadvantage of this known honing devices is that it has a relatively large overall length between the clamping end of the tool spindle and the work zone. Consequently, the shank of the honing tool tends to skew and vibrate during machining when its work zone enters the bore in the conventional gimbal-mounted workpiece, and this impairs the machining accuracy and the service life of the honing tool. Furthermore, the flushing of the work zone at the bottom of the blind-hole bore is unsatisfactory, since, in flow terms, dead areas can occur here. For high precision machining it is essential that the abraded particles be flushed away from the machining zone immediately.
The object of the present invention is to avoid these disadvantages and provide a honing device for precision machining, by means of which relatively small bores, especially blind-hole bores, can be machined to an unusually high accuracy not attainable hitherto by honing, while at the same time ensuring that the tool has a long service life.
The coolant feed device according to the invention can be arranged immediately above the workpiece on a device plate. The honing tool can pass centrally through the coolant feed device, and the latter can receive guide and sealing elements which can come freely into alignment with the shank of the honing tool. During honing, the guide and sealing elements are then held in the aligned position by means of the coolant pressure. This ensures an extremely rigid and vibration-free guidance of the honing tool. The feeding of the coolant under high pressure inside the honing tool to the front end of the honing tool facing the workpiece bore and the return of the coolant via the return channel guarantee a precisely defined coolant circulation within the work zone. As a result, machining accuracy is improved considerably by means of the honing device according to the present invention, so that the device is particularly suitable for making blind-hole bores which have to be machined with high precision, such as, for example, the machining of bores in injection-pump parts.
Further features of the invention will be apparent from the description which follows.